<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* 
            outline-width 设置轮廓的宽度
            outline-color 设置轮廓的颜色
            outline-style 设置轮廓的样式
            设置轮廓时 样式outline-style必须要设置

            outline 简写属性
            属性值之间用空格隔开，顺序无所谓
            最简便的写法 outline: solid
        */
        div {
            width: 100px;
            height: 100px;
            outline-width: 10px;
            outline-color: red;
            outline-style: solid;
            outline: 10px solid red;
            border: 10px blue solid;
            /* 边框在里面 轮廓在外面 */
        }
        input {
            /* border: none; */
            outline: none;
        }
    </style>
</head>
<body>
    <div></div>
    <input type="text">
</body>
</html>